1. Field of the Invention
The present invention relates to an air-intake device for an internal combustion engine, the device having a mechanism for reducing noises generated in a combustion chamber and propagated outside through the air-intake device.
2. Description of Related Art
An example of a device for reducing engine noises is disclosed in JP-A-2004-293365. The device includes a resonator attached to an intake air passage. A vibrating member is disposed at a boundary between the resonator and the intake air passage. The vibrating member is vibrated by sound pressure generated in a combustion chamber and propagated to the intake air passage. It is designed to offset the sound propagating through the intake air passage by vibrations of the vibrating member.
In this device, vibration frequencies of the vibrating member are adjusted by pushing the vibrating member with a stick so that noises desired to be eliminated are canceled by the vibrations of the vibrating member. However, an actuator for driving the stick has to be provided in this device, and it is difficult to precisely adjust the vibration frequencies of the vibrating member. In addition, the frequencies of the noises offset by the vibrating member vary depending on positions of the vibrating member in the air-intake passage.